class Compiler {
    constructor(vm) {
        this.el = vm.$el
        this.vm = vm
        this.compile(this.el)
    }

    // 编译模版，处理文本节点和元素节点
    compile(el) {
        let childNodes = el.childNodes;
        Array.from(childNodes).forEach(node => {
            // 处理文件节点
            if (this.isTextNode(node)) {
                this.compileText(node)
            } else if(this.isElementNode(node)) {
                // 处理元素节点
                this.compileElement(node)
            }

            // 判断node节点，是否存在子节点， 有则需要递归调用compile
            if (node.childNodes && node.childNodes.length) {
                this.compile(node)
            }
        })
    }

    // 编译元素节点，处理指令
    compileElement(node) {
       // 遍历所有的属性节点
       Array.from(node.attributes).forEach(attr => {
            let attrName = attr.name;
            if (this.isDireactive(attrName)) {
                // v-text --> text
                // v-on:eventType ->
                let [direactive, eventType] = attrName.substr(2).split(':')
                let key = attr.value
                this.update(node, key, direactive, eventType)
            }
       })
    }

    update(node, key, direactive, eventType){
        if (!eventType) {
            let updaterFn = this[direactive+'Updater']
            updaterFn && updaterFn.call(this, node, this.vm[key], key)
        } else {
            let updaterFn = this[direactive+'Updater']
            updaterFn && updaterFn.call(this, node, eventType, key)
        }
    }

    // 处理v-text指令
    textUpdater(node, value, key) {
        node.textContent = value
        new Watcher(this.vm, key, (newValue) => {
            node.textContent = newValue
        })
    }

    // 处理v-html指令
    htmlUpdater(node, value, key) {
        node.innerHTML = value;
        new Watcher(this.vm, key, (newValue) => {
            node.innerHTML = newValue;
        })
    }

    // 处理v-on指令
    onUpdater(node, eventType, cbName) {
        node.addEventListener(eventType, this.vm[cbName])
    }

    // 处理v-model
    modelUpdater(node, value, key) {
        node.value = value
        new Watcher(this.vm, key, (newValue) => {
            node.value = newValue
        })
        // 双向绑定
        node.addEventListener('input', () => {
            this.vm[key] = node.value;
        })
    }

    // 编译文本节点，处理差值表达式
    compileText(node) {
        // console.dir(node)
        // {{ msg }}
        let reg = /\{\{(.+?)\}\}/
        let value = node.textContent
        if(reg.test(value)) {
            let key = RegExp.$1.trim();
            node.textContent = value.replace(reg, this.vm[key]);

            // 创建watcher对象，
            new Watcher(this.vm, key, (newValue) => {
                node.textContent = newValue
            })
        }
    }

    // 判断元素属性是否是指令
    isDireactive(attrName) {
        return attrName.startsWith('v-')
    }

    // 判断是否是文本节点
    isTextNode(node) {
        return node.nodeType === 3
    }

    //判断是否是元素节点
    isElementNode(node) {
        return node.nodeType === 1
    }
}